This project aims broadly at advancing our understanding of the mechanisms that affect orphaned children, in particular by comparing the importance of genetic relatedness and of social norms with respect to parenting behavior. Specifically, the project will aim at measuring (1) potential disadvantages in adulthood among individuals who lost their mother and/or father during childhood and among those who grew up in households caring for orphans;(2) the extent to which any orphan disadvantage depends on the kinship to the foster parents;and (3) the degree to which solidarity bonds between parents and children differ for fostered orphans v. biological children and vary across social environments. This research project is set in Cambodia, where many children lost one, and often both, parents during the 1975-79 crisis, in which nearly 25 percent of the entire population died, and uncharacteristically, middle-aged to older adults were hit particularly hard. The project entails the collection and analysis of data on these orphans and on their subsequent transition to adulthood. The sample will be drawn from a demographic surveillance system (DSS) that, encompassing entire communities, captures the most significant relationships among member households. Moreover, the DSS approach, which has been successfully implemented with earlier support from an R03, is combined here with the random-selection of communities to increase representatively, environment diversity and sample size. In particular, this design allows for the identification of former foster parents of orphans and of their own children. The project's longer term aims are to advance scientific knowledge on the interaction of biological and social determinants of the transition to adulthood, to expand traditional methods of data collection, and to contribute to research capacity-building in Cambodia. Orphan crises are expected in countries experiencing resurgence in adult mortality. Where this resurgence is driven by infectious diseases, the proportion of orphans who loose both parents in succession is particularly likely to increase. To maintain the health and welfare of these orphans and contribute to their successful transition to adulthood requires a comprehensive understanding of the mechanisms through which orphans are affected by, or protected from, the loss of one or both parents during childhood.